The ACLU is sounding the alarm about a patent application from Amazon that would pair a face surveillance program with a doorbell camera. The patent application, which was made public recently, describes a product that would let police or homeowners match the faces of people walking by the doorbell camera with a photo database of persons they deem “suspicious.” If a match occurs, the suspicious person’s face can be automatically sent to law enforcement.

Earlier this year, Amazon bought the smart-doorbell company Ring.

The surveillance system described in the patent is, well, kind of unsettling, and so naturally the ACLU is monitoring it as closely, as it will be monitoring our front porches. In a blog post, ACLU lawyer Jacob Snow, a former patent litigator who now works in the ACLU’s Technology & Civil Liberties department, lays out the case against this would-be doorbell watchdog:

“Amazon is dreaming of a dangerous future, with its technology at the center of a massive decentralized surveillance network, running real-time facial recognition on members of the public using cameras installed in people’s doorbells.”

If that’s enough to get you Googling “how to make tin foil hats,” Snow also notes that the patent application doesn’t limit the new tech’s use to facial recognition, but also includes “an arsenal of other biometrics, including fingerprints, skin-texture analysis, DNA, palm-vein analysis, hand geometry, iris recognition, odor/scent recognition, and even behavioral characteristics, like typing rhythm, gait, and voice recognition.”

That should be enough to make privacy-conscious members of Congress and civil liberties advocates more than a little nervous.

An Amazon spokesperson declined to comment. In the past, the company has emphasized that a patent application doesn’t necessarily mean a product is forthcoming and has criticized “patent speculation” by the media.